In the home construction industry, it is typical for windows to be constructed as independent, prefabricated units and installed in framed openings constructed in the exterior walls of the home. The exterior framing of the window units overlap the exterior of the housing wall around the framed openings and initially are sealed to prevent access of moisture. Over time the sealing material may deteriorate and allow some moisture to penetrate. This can result in deterioration of the wood framing and of housing structure below the framed opening. Accordingly, in many such structures it is the practice to install a sill pan flashing between the bottom of the prefabricated window unit and the underlying sill plate of the framing. The sill pan flashing is formed of a suitable plastic or metal material and serves to direct any collected water outward to the exterior of the siding. Examples of such sill pan flashing devices are shown in U.S. Pat. No. 1,677,130, U.S. Pat. No. 7,222,462, U.S. Pat. No. 7,673,426, and U.S. Pat. No. 8,443,554. A typical framed window opening includes a horizontal sill plate and spaced apart vertical elements, joined to opposite ends of the sill plate and extending upward therefrom. The upper ends of the vertical elements are joined to a header member, which extends horizontally between the vertical members and forms a closed opening, usually of rectangular configuration, in which a prefabricated window unit can be received. The elements comprising the framed opening typically may be formed of 2″×4″ lumber. In addition, a rough siding typically is secured to the exterior framing of the structure, and an opening is cut into the rough siding in the size and shape to coincide with the framed opening. The rough siding may be of ½″ or ¾″ plywood, for example.
A sill pan flashing of typical construction includes a sill cover arranged to extend over the full width of the sill plate, which forms the bottom member of the framed opening. The sill cover is tilted forwardly to allow to allow water to drain forwardly toward the exterior of the structure. Typically, a front flange extends downward a short distance from the front of the sill cover to guide the flow downward over the exterior shingles, siding or other outer surface of the finished structure. The front flange typically extends laterally a few inches beyond the sides of the opening so as to cover a small front area of the rough siding. Portions of the front flange also extend upwardly a few inches above the level of the sill plate at each side of the opening. Side flanges also extend upward a few inches from each end of the sill cover and overlie lower portions of the vertical framing members. The side flanges are joined at their front vertical edges with the upwardly extending portions of the front flange to form rigid corners structure at opposite sides of the framed opening.
It is standard construction practice to dimension the rough-framed window openings to dimensions somewhat larger than the standard dimensions of the prefabricated windows to be inserted therein. Window manufacturers recommend that the opening defined by the framing be a half to three-quarters inch larger than the nominal size of the window. In actual practice it is common for the dimensions of the rough framing to vary significantly from the recommended tolerances, anywhere from a half to three-quarters inch smaller to more than an inch larger than recommended. This presents a problem with respect to the installation of the sill pan flashings, because the required width of the flashing, in order to fit snuggly between the vertical elements of the frame, may be different for each of many framed openings that are “nominally” of the same size. Heretofore, this commonly has been dealt with by forming the sill pan flashings in two or three (sometimes more) pieces, which are assembled in the field to fit the individual openings. A two-piece assembly, for example, is made to fit the largest opening expected to be encountered in the field for a given nominal size window unit. For a prefabricated window unit of 24″ nominal width for example, the specified framing opening may be 24.5″-24.75″. However, the actual opening made by the carpenters at the job site might range from as large as 25.5″ or greater to as small as 24.0″. Thus, a conventional two-piece sill pan flashing, intended for a window unit of nominal 24″ width, is dimensioned so that the pieces have a total width substantially greater than the anticipated maximum opening of 25.5″, enabling the two pieces to be assembled in the field in partially overlapping relation to fit a range of opening sizes. Typically, a sealant is applied in the field where the two pieces overlap, to avoid leakage at the interface between the parts.
The above described procedures, while enabling the flashing to be fit suitably to the framed opening, have important disadvantages. Among others, the individual installation of the two (or more) components, and the sealing of the interface(s) between them consumes extra labor time and thus adds to the cost of construction. Additionally, construction sites are often somewhat chaotic, and it is not uncommon for the individual components of a multi-part flashing assembly to become separated at the job site, so that all of the mating parts may not be readily available when the worker is ready to install them. Also, where application of a sealant is required, as it always is the sill pan has more than one piece, a worker may not have a caulking gun readily at hand when needed and may have to interrupt the assembly to find and fetch it.
It has been proposed heretofore to fabricate a sill pan flashing in one piece, sized suitably at a width greater than the maximum expected width of the rough opening. Although the proposed one-piece flashing can be shipped to the job site as a single unit, it must be cut into two parts at the job site in order to fit the opening. The then two-piece assembly is overlapped and sealed during installation in the same manner as the above-described multi-piece assemblies, with the addition of the cutting operation and the requirement of the necessary tools to perform the cutting operation. Such a proposal is found in the Broad et al. U.S. Pat. No. 7,673,426.
There thus remains a long-felt need for an improved form of sill pan flashing that can be fabricated, shipped and installed in one piece with attendant reduction in labor costs and inventory issues, and with improved performance.